A laser beam has good collimation as well as a capability for high power and intensity. Due to these properties, laser generators are widely applied in modern industries, such as in highly collimated light sources used in laboratories, laser pens for presentations, as well as laser light sources for reading or burning compact discs, laser light sources for the laser mouse, laser light sources for different types of measurement instruments, laser light sources for the display field, laser light sources for fiber communication, laser light sources for instruments used in the medical field, and so on.
When light is transmitted in an optical fiber, since the incident angle on the surface of the fiber is larger than the critical angle of the fiber material, the surface of the fiber totally reflects the light inside the optical fiber. When the totally reflected light is again transmitted to the surface of the optical fiber, the afore-described condition of the incident angle being larger than the critical angle is still met, and thus light is again totally reflected by the surface of the optical fiber. The total reflection above refers to light being totally reflected without loss. Accordingly, the light entering one end of the optical fiber may be transmitted to another end of the optical fiber with low energy loss, and this rate of energy loss is lower than the energy loss incurred by electrons transmitted in wires due to resistance.
As optical fiber techniques matured in recent years, the optical fiber is being applied in the laser field, in which light is transmitted in the optical fiber and reflectors are configured at two ends of the optical fiber, so as to form a resonant cavity. Since the optical fiber is flexible, when the fiber is coiled into a plurality of loops, a resonant cavity of great length may be formed without causing the size of the entire optical system to become overly large. A resonant cavity having this length is hard to achieve with conventional laser techniques.
However, generally speaking, a laser system typically generates a laser beam of one wavelength. Therefore, when laser beams of two or more wavelengths are required at the same time, two laser systems are needed. As such, the costs for purchasing the necessary instruments and equipments drastically increase. Moreover, the application range of a single laser system is also limited.